In recent years, light-emitting diode driving semiconductor devices for driving a light-emitting diode (hereinafter, referred to as an LED) and light-emitting diode driving apparatuses having the same are developed and put in practical use. In particular, a large volume of lighting devices, such as an LED bulb having a white LED as a light source, are manufactured. Moreover, various driver circuits which properly drive an LED are proposed (e.g., see Patent Literatures (PTLs) 1 to 3).
A conventional light-emitting diode driving apparatus disclosed in PTL 1 is an apparatus which has a non-isolated flyback converter circuit structure, and includes a transformer for transforming a DC voltage into energy.
A conventional light-emitting diode driving apparatus disclosed in PTL 2 has a buck converter circuit structure. For example, the light-emitting diode driving apparatus includes a buck converter which includes a switching element Q21, a driver circuit 213, a rectifying element D22, a choke coil L23, and a smoothing condenser C24. Here, the buck converter is, particularly, a high-side buck converter in which a switching element is disposed on the high side of an input voltage.
To construct a non-isolated circuit, the use of a buck converter is advantageous in efficiency or cost, as compared to a flyback converter.
A conventional light-emitting diode driving apparatus disclosed in PTL 3 includes a buck converter as with PTL 2. The buck converter is, particularly, a low-side buck converter in which a switching element is disposed on the low side (reference potential) of an input voltage.